It is well known in IV care art that turbulent “start-stop” or “push-pause” flushing of IV catheters, e.g. central venous catheters, has become an accepted method for purging matter from catheters and, thereby, preventing build-up of deposits of blood, blood residue and IV drugs within a catheter. Such build-up can cause partial or complete blockage of the fluid pathway in a catheter system, requiring expensive and potentially dangerous methods for purging the catheter or necessitating a total catheter exchange. Often, such blockages lead to interruptions in therapy (e.g. IV therapy) that may compromise patient care. Further, build-up of residue within a catheter can also increase infection risk by providing a breeding medium for microorganisms. For this reason, push-pause flushing is traditionally, and more or less universally, taught to healthcare workers.
Push-pause (or turbulent) flushing simply requires a clinician to alternately increase and decrease an associated infusion rate during flushing. However, efficiency and success of catheter purging using push-pause flushing is well known to be completely dependent upon individual awareness, compliance and technique and a successful purging operation is often incomplete and problematic. For this reason, many users may not use such turbulent flushing effectively while others, due to lack of knowledge or perception of value, may not use it at all.
Also, other than using turbulence for catheter clearance, syringes, pumps and other fluid forcing mechanisms associated with IV infusion are substantially operated in a laminar flow domain. When pulsatile flow is used, pressure and flow characteristics are constrained well below those turbulent and volumetric flow levels required for effective catheter purging.
In the wide spectrum of syringe design, it is common to find art which provides periodic stops of various types and kinds for syringe plungers. Generally, many such stops are employed to aid in accurately measuring and dispensing a portion of a syringe fill. Once such stops are reached, it is common for the plunger to be released to thereby permit controlled and substantially laminar flow to the next stop. In other words, such stops are generally released without a calculated, intentional force to propel the stopper with sufficient force for catheter purging. Other stops are commonly used to limit a syringe to a single use. Generally, these stops are hard and cannot be reasonably overcome, as is common in single-use hypodermic syringes.
An example of a plunger stop for the purpose of limiting injection of fluid from a syringe is found in U.S. Pat. No. 4,642,102 issued Feb. 10, 1987 to Hirofumi Ohmori (Ohmori). Ohmori discloses stops which engage recesses in a plunger rod associated with a plunger to interrupt discharge from the syringe. After each stop, the plunger rod is strictly stopped such that no excessive force is able to drive the plunger rod further. Similarly U.S. Pat. No. 5,024,661 issued Jun. 18, 1991 to Harry Wender (Wender) discloses a single use syringe having recesses along a plunger rod.
U.S. Pat. No. 5,318,544 issued Jun. 7, 1994 to John Drypen, et al. discloses a metering syringe having a plunger rod containing a plurality of stop surfaces. The stop surfaces are spaced apart to define a predetermined dose volume. Plunger rod rotation relieves each stop to permit further dispensing.
U.S. Pat. No. 5,059,181 issued Oct. 22, 1991 to Robert. B. Agran (Agran) also discloses a syringe assembly having recesses in a plunger rod which are used to retard a second rearward displacement of the plunger rod associated with a second use of the syringe assembly. In similar manner, U.S. Pat. No. 5,084,017 issued Jan. 28, 1992 to John Maffetone (Maffetone) discloses a single use syringe having a notched plunger rod. The syringe of Maffatone is taught to operate smoothly, but to dissemble itself at the completion of a single use cycle.
U.S. Pat. No. 5,280,030 issued Oct. 5, 1993 to Cesar G. Corsich, et al. (Corsich) discloses a hypodermic syringe having a blockable piston capable of preventing recharge and reuse under some conditions.
U.S. Pat. No. 5,328,476 issued Jul. 12, 1994 to James Bidwell (Bidwell) discloses a single-use hypodermic syringe apparatus. Rachet grooves in an associated plunger rod are used as lock members such that when plunger is fully inserted or reinserted into a casing, the plunger is prevented from being withdrawn relative to the casing.
U.S. Pat. No. 6,283,941 issued Sep. 4, 2001 to Joel Schoenfeld, et al. (Schoenfeld) discloses a rod-like syringe plunger having a plurality of bead-like rachet teeth. Schoenfeld also discloses a single use syringe. Of particular note is the statement, “It is a further object of the present invention to provide a single use syringe which has a smooth mechanical operation and a plunger retraction force less than the industry maximum standard” Such objectives are commonly held in the syringe art for manipulating syringe plunger rods.
U.S. Pat. No. 5,891,052 issued Apr. 6, 1999 to Paul L Simmons (Simmons) teaches a syringe plunger sabot and sabot lock disposed within a syringe body, the sabot lock mechanism being selectively moveable between a locked and unlocked position. Thereby an engagement is made to create a vacuum for extracting material into the syringe body.
U.S. Pat. No. 6,488,651 issued Dec. 3, 2002 to David Paul Morris et al. (Morris) discloses a mixing syringe having a plunger rod dasher which permits flow within the barrel for communicating material to be mixed with material in a more proximal chamber. Other cylindrical barriers provide within chamber defining spaces which are selectively displaced by movement of the plunger rod. Other than resistances of fluid dynamics and friction (and stiction), no other retarding forces are taught.
U.S. Pat. No. 6,579,269 B1 issued Jun. 17, 2003 to Gennady I. Kleyman (Kleyman) discloses a dose measuring syringe. A plunger rod, as taught in Kleyman, has formations which increase resistance to displacement of the plunger rod and to produce an audible sound corresponding to a predetermined volume for a measured dose. Even so, there are no teachings in Kleyman for providing momentary stops which produce a predetermined amount of turbulent flow in a catheter.
U.S. Pat. No. 5,685,864 issued Nov. 11, 1997 to Laurence M. Shanley, et al. (Shanley) discloses an aspiration syringe device which operates oppositely to aspirate rather than discharge into a connected site. A right angle stem of an associated plunger is equipped with spaced flanges. Interior of the syringe barrel is equipped with at least one stop. When a flange is contiguous with a stop, advancement of the plunger is prohibited. Rotation of the plunger permits further advancement.
U.S. Pat. No. 4,995,869 issued Feb. 16, 1991 to Martin McCarthy (McCarthy) discloses a single-use hypodermic syringe. A syringe barrel according to McCarthy has an interior undulating surface over which a skirt rides rearward under direction of a proximally directed manual force. While it seems apparent that the undulations will cause a pulsation in flow while discharging fluids via a patient needle, it is clear that there are no related teachings for creating turbulent flow in a catheter, a subject untouched in McCarthy.
Generally, in summary, prior art, of which art cited above is an example, discloses and teaches plunger rod having slots, grooves and rachet teeth are for providing obstructions used for measuring predetermined volumes of dispensed fluids or for stops associated with providing single use syringes. Just as clinician-dependent generation of push-pause flow is problematic, all such art is void of teachings which assure successful creation of turbulent flow for clearing an associated attached catheter system. Such is the specific and precise purpose of the present invention.